# Patent

## Title
Same layer microelectronic circuit patterning using hybrid laser projection patterning (LPP) and semi-additive patterning(SAP)

## Abstract

In some embodiments, same layer microelectronic circuit patterning using hybrid laser projection patterning (LPP) and semi-additive patterning (SAP) is presented. In this regard, a method is introduced including patterning a first density region of a laminated substrate surface using LPP, patterning a second density region of the laminated substrate surface using SAP, and plating the first and second density regions of the laminated substrate surface, wherein features spanning the first and second density regions are directly coupled. Other embodiments are also disclosed and claimed.

## Background
FIELD OF THE INVENTION
Embodiments of the present invention generally relate to the field of integrated circuit package substrates, and, more particularly to same layer microelectronic circuit patterning using hybrid laser projection patterning (LPP) and semi-additive patterning (SAP).
BACKGROUND OF THE INVENTION
Reductions in the size and pitch of integrated circuit devices require advancements in the manufacture of IC package substrates. The use of lasers is becoming more common for patterning substrates. Disadvantageously, the use of laser projection patterning to pattern a substrate layer tends to cost much more than semi-additive patterning.



BRIEF DESCRIPTION OF THE DRAWINGS
The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements, and in which:
FIG. 1 is a graphical illustration of an overhead view of a package substrate surface, in accordance with one example embodiment of the invention;
FIGS. 2A-2J are graphical illustrations of a cross-sectional view of a partially formed IC package substrate, in accordance with one example embodiment of the invention; and
FIGS. 3A-3K are graphical illustrations of a cross-sectional view of a partially formed IC package substrate, in accordance with one example embodiment of the invention.



DETAILED DESCRIPTION
In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that embodiments of the invention can be practiced without these specific details. In other instances, structures and devices are shown in block diagram form in order to avoid obscuring the invention.
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.
FIG. 1 is a graphical illustration of an overhead view of a package substrate surface, in accordance with one example embodiment of the invention. In accordance with the illustrated example embodiment, package substrate 100 includes one or more of necking region 102, main routing region 104, die shadow 106, and signal trace 108.
Necking region 102 represents a region on the surface of substrate 100 where signals, such as signal trace 108 routed to escape from an integrated circuit die, which would occupy die shadow 106. In one embodiment, signal traces 108 are input/output (I/O) signals that are routed from outer bumps of the integrated circuit die. Necking region 102 generally has a higher density than main routing region 104. In one embodiment, necking region 102 contains line widths of about 9 micrometers and spaces of about 12 micrometers. In one embodiment, main routing region 104 contains line widths of greater than about 14 micrometers and spaces of greater than about 14 micrometers. In one embodiment, signal traces 108 have a length within necking region 102 of a few millimeters. As shown, necking region 102 is slightly larger than die shadow 106.
As described in embodiments hereafter, same layer microelectronic circuit patterning may use laser projection patterning (LPP) in necking region 102 and semi-additive patterning (SAP) in main routing region 104. Signal traces 108 are seamlessly spanned (for example, continuous copper traces) across both regions.
FIGS. 2A-2J are graphical illustrations of a cross-sectional view of a partially formed IC package substrate, in accordance with one example embodiment of the invention. FIG. 2A depicts substrate 200 after build-up dielectric 202 is laminated on a core or existing build-up layers, including pads 204, followed with pre-cure of the dielectric. The dielectric materials are generally polymer based and filled with dispersed silica fillers, such as commercially available fillers and a variety of other materials.
FIG. 2B depicts substrate 200 after laser via 206 drilling over the whole pattern and desmear. The desmear process comprises of swelling the walls of via 206 using alkali solution such as sodium hydroxide, and them etching with highly reductive chemical such as permanganate based aqueous solution.
FIG. 2C depicts substrate 200 after LPP ablation to form a blank pattern 208 in dielectric 202 at the necking region, such as necking region 102. The necking region is normally a little larger than the die shadow, containing fine lines and spaces for I/O signal routing and fan-out.
FIG. 2D depicts substrate 200 after electroless copper seed layer plating followed with electrolytic copper plating 210 to specific thickness, for example, 5-20 um. The necking area is covered with over-plated copper 212 on the dielectric top surface.
FIG. 2E depicts substrate 200 after removal of over-plated copper 212 using a selection of methods such as CMP, mechanical polishing, chemical etching or the combination of the above. After this step the necking region of the pattern is completed.
FIG. 2F depicts substrate 200 after electroless copper 214 plating and dry film resist (DFR) 216 lamination.
FIG. 2G depicts substrate 200 after DFR 216 is patterned with conventional litho process (exposure and development). The necking region patterned is covered with DFR 216, except for outer portions 217 of the necking region.
FIG. 2H depicts substrate 200 after electrolytic copper 218 plating to specific thickness, for example, 5-20 um. In this way, the main routing region is plated on top of the outer portions 217 of the necking routing region.
FIG. 2I depicts substrate 200 after DFR 216 is stripped using alkali solutions such as aqueous sodium carbonate solution. Organic type of solution can also be used.
FIG. 2J depicts substrate 200 after chemical etching to remove the electroless copper seed layer 214 to form the whole pattern.
In one embodiment, package substrate 200 is coupled on surface 220 with an integrated circuit die such as a flip chip silicon die. In another embodiment, surface 220 is laminated with another dielectric layer as part of a continued build-up process.
FIGS. 3A-3K are graphical illustrations of a cross-sectional view of a partially formed IC package substrate, in accordance with one example embodiment of the invention. FIG. 3A depicts substrate 300 after build-up dielectric is laminated on core or existing layer, including pads 304, followed with pre-cure of the dielectric. The dielectric materials are generally polymer based and filled with dispersed silica fillers, such as commercially available fillers and a variety of other materials.
FIG. 3B depicts substrate 300 after a dielectric protrusion 306 is made on dielectric surface 307 at the necking region. This can be made by selectively laminating an added layer of dielectric, or by imprinting the dielectric layer laminated in step 1 with a pocket that corresponds to the protrusion to be formed.
FIG. 3C depicts substrate 300 after laser via 308 drilling over the whole pattern and desmear. The desmear process comprises of swelling the walls of via 308 using alkali solution such as sodium hydroxide, and them etching with highly reductive chemical such as permanganate based aqueous solution.
FIG. 3D depicts substrate 300 after LPP ablation to form a blank pattern 310 within protrusion 306 at the necking region. The neck region is normally a little larger than the die shadow, containing fine lines and spaces for I/O signal routing and fan-out.
FIG. 3E depicts substrate 300 after electroless copper seed layer 312 plating over the whole pattern.
FIG. 3F depicts substrate 300 after DFR 314 lamination over the whole pattern.
FIG. 3G depicts substrate 300 after DFR 314 is patterned with conventional litho process (exposure and development). The necking region pattern 310 is exposed after litho. Main region pattern 316 outside the necking region is defined.
FIG. 3H depicts substrate 300 after electrolytic plating 318 of the whole pattern to specific thickness, for example, 5-20 um. The necking area is covered with over-plated copper 320 on the top surface of the dielectric layer.
FIG. 3I depicts substrate 300 after removal of over-plated copper 320 using a selection of methods such as chemical mechanical polishing (CMP), mechanical polishing, chemical etching or the combination of the above. After this step the necking region of the pattern is completed.
FIG. 3J depicts substrate 300 after DFR 314 is stripped using alkali solutions such as aqueous sodium carbonate solution. Organic type of solution can also be used.
FIG. 3K depicts substrate 300 after chemical etching to remove the electroless copper seed layer 312 to form the whole pattern.
In one embodiment, package substrate 300 is coupled on surface 322 with an integrated circuit die such as a flip chip silicon die. In another embodiment, surface 322 is laminated with another dielectric layer as part of a continued build-up process.
In the description above, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. In other instances, well-known structures and devices are shown in block diagram form.
Many of the methods are described in their most basic form but operations can be added to or deleted from any of the methods and information can be added or subtracted from any of the described messages without departing from the basic scope of the present invention. Any number of variations of the inventive concept is anticipated within the scope and spirit of the present invention. In this regard, the particular illustrated example embodiments are not provided to limit the invention but merely to illustrate it. Thus, the scope of the present invention is not to be determined by the specific examples provided above but only by the plain language of the following claims.

## Claims

1. A method comprising:
forming a dielectric protrusion on a laminated substrate surface, the dielectric including a necking region and a main routing region, the necking region including an area within a footprint of a die to be situated on the dielectric, and the main routing region contiguous with the necking region and extending outwardly therefrom;
ablating only the dielectric in the necking region with laser projection patterning (LPP);
plating the main routing region and the necking region with copper;
removing over-plated copper from the main routing region and the necking region;
electroless copper plating over the main routing region and the necking region;
patterning the main routing region and the necking region on the dielectric with dry film resist (DFR);
plating the main routing region such that a routing density in the necking region is greater than a routing density in the main region; and
removing the DFR.

2. The method of claim 1, wherein forming a dielectric protrusion on a laminated substrate surface comprises selectively laminating an added layer of dielectric.

3. The method of claim 1, wherein forming a dielectric protrusion on a laminated substrate surface comprises imprinting the substrate surface with a pocket that corresponds to the protrusion to be formed.

4. The method of claim 1, wherein plating the main routing and necking regions comprises over-plating the necking region.

5. The method of claim 4, further comprising removing the over-plated copper on top of the necking region.

6. The method of claim 1, wherein plating the main routing and necking regions comprises electrolytic copper plating to a thickness of between about 5 and about 20 micrometers.

7. The method of claim 1, wherein plating the main routing and necking regions comprises plating features that span the main routing and necking regions in a same electrolytic plating step.